The Parent-Infant Development Service (PIDS) is an interdisciplinary program--including psychiatry, psychology, social work, and pediatrics--of therapeutic intervention and clinical research. Drawing from a patient population of low socio-economic status, predominantly black families, PIDS is designed to test the efficacy of intervention in disturbances of interaction between parent(s) and their infant (at intake newborn to 18 months of age). Either the parent or infant can be the identified patient at intake. PIDS' therapeutic orientation is psychodynamic and aimed at various levels of the individual and family systems. Five treatment modalities are included: (1) parent-infant interaction treatment; (2) group therapy for parents; (3) family treatment; (4) infant/toddler group therapy; and (5) individual treatment. Using quantitative, single-case methodology, but incorporating a non-treatment comparison group, the research is designed to assess the impact of the intervention of family-infant interactions, parent functioning, infant development and the place of the family in its social setting. In addition to contributing to theory and to its integration with practice, PIDS' long-term objects are to develop effective services, assessment procedures and research strategies that can be applied to a variety of settings in working with disturbances in parent-infant relationships.